The present invention relates to a method for operating an internal combustion engine, for example, of a motor vehicle, in which a mixture of air and fuel is delivered from a tank by an activated carbon filter and by a tank venting valve to a combustion chamber. The present invention also relates to a control device for an internal combustion engine and an internal combustion engine, for example, for a motor vehicle.
In vehicles having gasoline-driven engines, a varying quantity of fuel vapor may be present in the fuel tank, depending on fuel temperature, fuel grade, and external pressure. In fuel-injected gasoline engines, the fuel vapor may be collected in an activated carbon filter and then, in tank venting phases provided therefor, mixed by an electrically activatable tank venting valve into the air flow taken into the engine.
The tank venting system, for example, may keep the overall combustion mixture at a desired richness irrespective, to the greatest degree possible, of how saturated the activated carbon filter is with hydrocarbons. For this purpose, the quantity of fuel injected may be correspondingly reduced, when the tank venting valve is open.
Due to a balance of the instantaneous mass gas flow through the tank venting valve, the instantaneous fuel flow required by the engine, the instantaneous lambda value and the mixture correction already performed by the lambda control system, an instantaneous hydrocarbon concentration of the regeneration gas flow (also called the xe2x80x9cloadingxe2x80x9d) may be adapted and the quantity of fuel injected may be corrected or controlled, in an open- and/or closed-loop fashion, on the basis of the instantaneous hydrocarbon concentration. The adaptation of the hydrocarbon concentration of the regeneration gas flow should not occur arbitrarily quickly, since the delay time of the distance between the respective injection valve and the lambda probe in the exhaust gas flow may limit the maximum adaptation speed.
During the adaptation process, the instantaneous hydrocarbon concentration of the regeneration gas flow may change until the lambda control system reaches its neutral value xcex=1 or until the mixture deviation becomes zero.
The physical hydrocarbon concentration profile may not be in a steady-state. Concentration spikes may occur, for example, when the activated carbon filtration system does not possess sufficient buffering and the regeneration gas mass flow is changing rapidly, for example, after regeneration off times. Abrupt transient deviations from the stoichiometric air/fuel ratio, that is, from a value xcex=1, may be expected in such a case.
It is an object of the present invention to provide a method for operating an internal combustion engine that may consider transients that occur upon rapid changes in the regeneration gas mass flow.
This object may be achieved, according to an exemplary embodiment of the present invention, by controlling the tank venting valve in an open- and/or closed-loop fashion, as a function of a tank gas evolution model.
This object may also be achieved, according to another exemplary embodiment of the present invention, by controlling the tank venting valve in an open- and/or closed-loop fashion, as a function of an activated carbon filter model.
The object may also be achieved, according to yet another exemplary embodiment of the present invention, in corresponding fashion, by a control device and an internal combustion engine.
In a control system for considering the instantaneous hydrocarbon concentration in the regeneration gas flow, the system calculating a correction value for correcting the injection quantity, a tank gas evolution model adapting the hydrocarbon gas production in the tank and/or a model of the activated carbon filter is provided, with the aid of the tank gas evolution model and/or the model of the activated carbon filter, to predict the hydrocarbon concentration at the location of the tank venting valve and, on the basis of the prediction, to generate the correction value quickly and reliably, after regeneration off times, so that lambda deviations during dynamic engine operation may be reduced, so that they are not perceptible, even by a sensitive driver.
An exemplary method according to the present invention may be implemented as a control element for a control device of an internal combustion engine, for example, of a motor vehicle. A program that is executable on a computing device, for example, on a microprocessor, and suitable for executing the exemplary method according to the present invention, may be stored on the control element. In this way, therefore, an exemplary embodiment of the present invention may be implemented by a program stored on the control element, so that the control element equipped with the program performs the same way as the exemplary according to the present invention. An electrical storage medium, such as, for example, a read-only memory or a flash memory, may be used, for example, as the control element.